It should be fine traffic wise. There's really no end to the things you can do. Usually it's still not too cold and sometimes it's even decent weather. Coastal Maine is great, and I kind of like the ocean in the winter. You can drive the coast between Portland and Boston and just stop at random Maine towns. NYC is fun that time of year although very crowded. Happy to provide any other advice or recommendations. I'm very familiar with everything from Portland ME to DC.